This invention relates to a tape drive for use in a linear tape storage system represented by DLT (Digital Linear Tape) or LTO (Linear Tape Open) and, in particular, to a linear actuator which can be used as a head feed mechanism for moving a magnetic head used in the tape drive.
A linear tape storage system of the type has been developed as a backup for a computer system. A variety of linear tape storage systems have heretofore been proposed. For example, a digital linear tape drive as the DLT is disclosed in U.S. Pat. No. 5,862,014.
The digital linear tape drive is adapted to receive a tape cartridge having a single supply reel. The digital linear tape drive includes a take-up reel in the interior thereof. When the tape cartridge is received in the tape drive, a magnetic tape is pulled out from the tape cartridge to be wound up around the take-up reel through a head guide assembly. The head guide assembly serves to guide to a magnetic head the magnetic tape pulled out from the tape cartridge. The magnetic head exchanges information to and from the tape.
As disclosed in U.S. Pat. No. 5,793,574 for example, a tape drive typically comprises a generally rectangular housing having a common base. The base has two spindle motors. The first spindle motor has a permanently mounted spool permanently mounted to the base to serve as a take-up reel. The spool is dimensioned to accept a magnetic tape streaming at a relatively high speed. The second spindle motor is adapted to receive a removable tape cartridge.
The removable tape cartridge is manually or automatically inserted into the drive via a slot formed on a housing of the drive. When the tape cartridge is inserted into the slot, the cartridge is engaged with the second spindle motor. Prior to rotation of the first and the second spindle motors, the tape cartridge is connected to the permanently mounted spool by means of a mechanical buckling mechanism. A number of guide rollers are positioned between the tape cartridge and the permanently mounted spool and guide the magnetic tape as it streams at a relatively high speed back and forth between the tape cartridge and the permanently mounted spool.
The tape drive further comprises a head assembly. The head assembly is positioned between the spool and the tape cartridge along a tape path defined by a plurality of rollers. During operation of the tape drive, the magnetic tape streams between the spool and the tape cartridge along the tape path, coming into close proximity to the head assembly during streaming. An example of the head assembly is disclosed in U.S. Pat. No. 5,793,574 mentioned above. On the other hand, Japanese Unexamined Patent Publication No. 2000-149491 (JP 2000-149491 A) discloses an example of the tape cartridge to be received in the digital linear tape drive.
In order to move the head assembly up and down in a widthwise direction of the magnetic tape, the tape drive further includes a head feed mechanism. For example, the head feed mechanism comprises a threaded shaft, i.e., a lead screw as disclosed in U.S. Pat. No. 5,793,574 mentioned above. By rotating the lead screw, the head assembly is linearly moved up and down. The head feed mechanism of the type is herein referred to as a xe2x80x9cmechanical linear actuatorxe2x80x9d.
In the mechanical linear actuator, position control of the head assembly is carried out by so-called open-loop control. Therefore, it is difficult to controllably bring the head assembly to a desired position with high accuracy.
In view of the above, the present inventors have proposed a head feed mechanism for moving a head assembly up and down by electromagnetic force. The head feed mechanism of the type will herein be referred to as an xe2x80x9celectromagnetic linear actuatorxe2x80x9d.
In the electromagnetic linear actuator, position control of the head assembly can easily be carried out by closed-loop (feedback) control. It is therefore possible to controllably bring the head assembly to a desired position with high accuracy.
However, the electromagnetic linear actuator requires a plurality of guide shafts for guiding the movement of the head assembly and a position sensor for detecting a current position of the head assembly. It is therefore difficult to reduce the number of components and the number of assembling steps and to save a mounting space occupied by the electromagnetic linear actuator.
It is therefore an object of this invention to provide an electromagnetic linear actuator which is reduced in number of components and in number of assembling steps and which requires a small mounting space.
It is another object of this invention to provide a tape drive comprising the above-mentioned electromagnetic linear actuator.
Other objects of the present invention will become clear as the description proceeds.
According to an aspect of the present invention, there is provided an electromagnetic linear actuator which comprises a fixed portion having a predetermined axis, a movable portion holding an object, a single guide shaft coupled to the fixed portion and the movable portion for guiding the movable portion to be movable with respect to the fixed portion only along the predetermined axis, and a position sensor coupled to the fixed portion and the movable portion for detecting a current position of the movable portion with respect to the fixed portion. The position sensor is cooperated with the single guide shaft to inhibit rotation of the movable portion around the predetermined axis.
According to another aspect of the present invention, there is provided a tape drive which comprises the above-mentioned electromagnetic linear actuator and a head assembly as the object held by the movable portion.